1. Field of the Invention
The present invention relates to a manufacture method for photovoltaic module.
2. Description of the Prior Art
A photovoltaic module has a construction wherein a plurality of solar cells are connected in series and/or in parallel by means of wiring members electrically connected to electrodes on front and back sides thereof. In the manufacture of the photovoltaic module, the conventional practice is to use solder for connecting the electrodes of the solar cells with the wiring members. The solder is widely used because of its excellent connection reliability including conductivity, bonding strength and the like.
From an environmental standpoint and the like, on the other hand, the solar cells also employ a wiring connection method not relying on the solder. There is known a method, for example, which uses a conductive adhesive film to interconnect the solar cells and the wiring material. Such a method is disclosed in, for example, United States Patent Publication No. 2009/0288697A1.
To connect the wiring material using the conductive adhesive film, the conductive adhesive film first need be pasted on a collector electrode of the solar cell. The conductive adhesive film is normally wound on a reel. A conductive adhesive sheet is unwound from the reel and an unwound portion of the sheet is pressure bonded to the solar cell by means of a film pasting device. Thus, the conductive adhesive film is pasted on the collector electrodes of the solar cells.
FIG. 12 is schematic perspective view showing an arrangement of the film pasting device. As shown in FIG. 12, the device comprises a conductive adhesive film feeding reel 200 having a conductive adhesive film sheet 50 wound thereon, and a carrier film take-up reel 201. The conductive adhesive film sheet 50 unwound from the feeding reel 200 is advanced to the carrier film take-up reel 201 by means of guide rolls 202, 202 via a pasting stage to past the film sheet on a solar cell 1. A conductive adhesive film 5 is pasted on a predetermined portion of the solar cell 1.
Before reaching the pasting stage, the conductive adhesive film sheet 50 is half-cut by a cutter 203 such that only an adhesive layer thereof is cut to a length in which the film sheet is pasted on the solar cell 1.
At the pasting stage, the conductive adhesive film sheet is pressed against the solar cell 1 at a predetermined pressure. Subsequently, the conductive adhesive film 5 is peeled off a carrier sheet and pasted on the solar cell 1. The carrier sheet is advanced from the guide roll 202 to the carrier film take-up reel 201 so as to be wound thereon. An apparatus has been contemplated which employs such film pasting devices for pasting the films on plural places in the apparatus. Such a method is disclosed in, for example, JP2004-78229(A).
A single apparatus having a mechanism for pasting the conductive adhesive films on upper and lower sides of a substrate negates the need for turning over the substrate of the solar cell requiring the films to be pasted on the upper and lower sides thereof. This makes it possible to reduce tact time.
However, the above-described method has the following problems because it requires as many conductive adhesive film feeding reels as the pasting stages of the pasting devices.
Firstly, the increase of the pasting positions leads to the increase of the feeding reels and thence, cost increase. Furthermore, a problem exists that the number of pasting lines is limited by the number of feeding reels.
Another problem is that the choices of width of the conductive adhesive film depend upon vendor's performance and hence, the width of the conductive adhesive film cannot be decreased from a given width. That is, the conductive adhesive film having too small a width cannot be wound on the reel. As it now stands, the conductive adhesive film must have a width of about 1.0 mm or more to be wound on the reel.
By the way, it is desired to reduce the width of the wiring material because the wiring material bonded to a light-incident side of the solar cell blocks the incident light. In a case where a wiring material having a width of 0.5 mm is used, for example, the conventional practice is to bond the wiring material with a conductive adhesive film having a width of 1.0 mm. As thermally set, the conductive adhesive film becomes tinted so that the light is shielded by the tinted portion of the film. Even though the 0.5 mm-wide wiring material is used, the light is shielded by the 1.0 mm-wide conductive adhesive film, which makes it impossible to increase light use efficiency.